Background/Aims: Previous studies have shown that the prevalence of abnormal acid reflux in fibrotic lung disease patients is high, and in particular, patients with secondary pulmonary fibrosis show higher esophageal acid exposure than normal controls. There are also some findings that, in patients with pathological reflux, pulmonary fibrosis may develop. The aim of this study is to investigate if pulmonary fibrosis is involved in the pathogenesis of chronic cough due to Gastroesophageal Reflux.